The present invention relates to a vehicle equipped with an automatic cruise control system, and more particularly to a vehicle with an automatic cruise control system having an automatic acceleration mode.
Cruise control systems for automotive vehicles have been available for years. Typically, for the basic systems, the vehicle driver attains the desired vehicle speed and initiates the cruise control system at a driver selected set speed. The vehicle then travels at the set speed unless the driver applies the brakes or turns off the system. With advances in vehicle electronics and sensor technology, adaptive cruise control (ACC) systems are becoming available that not only maintain the set vehicle speed, but also include an object sensing technology, such as radar, laser or other type of sensing system, that will detect an in-path vehicle. If the host vehicle is following too closely behind an in-path vehicle, the ACC will automatically reduce the host vehicle speed (by reducing the throttle and/or applying the brakes) sufficiently to obtain a predetermined safe following interval (which may be based on following distance and/or following time). The ACC will then continue to maintain the safe following interval.
Once the slower moving in-path vehicle moves out of the path, or speeds up sufficiently, and no other new in-path vehicle is detected, the host vehicle will automatically begin accelerating back up to the driver selected set speed-an auto-resume function. While the auto-resume is convenient for the driver, the driver may feel a sense of alarm if the vehicle is in heavy traffic and the automatic acceleration is too fast. But, on the other hand, if the automatic acceleration is set at a low rate (to avoid the feeling of alarm), then, when the host vehicle is traveling in light traffic and begins the automatic acceleration, the driver may be impatient with the slow rate of acceleration.
Thus, it is desirable for a vehicle with an ACC system and auto-resume to accelerate appropriately for the level of traffic around the vehicle in order to minimize driver unease with a high rate of acceleration in heavy traffic and impatience with a low rate of acceleration in light traffic.
In its embodiments, the present invention contemplates a method of operating a host vehicle having adaptive cruise control comprising the steps of: operating the host vehicle in the adaptive cruise control mode at a preset speed; encountering an in-path vehicle in the path of the host vehicle; slowing the host vehicle to maintain a predetermined vehicle following interval; sensing when the in-path vehicle is not in the path of the host vehicle such that the host vehicle may begin to return to the preset speed; beginning automatic acceleration mode; determining a traffic density adjacent to and in front of the host vehicle; and accelerating at one of at least two predetermined acceleration rates based upon the determined traffic density.
The present invention further contemplates an automatic cruise control system for a host vehicle. The automatic cruise control system includes an object sensing system that includes at least one object detector capable of detecting other vehicles in front of and adjacent to the host vehicle, a set speed selector capable of selecting a set speed for the host vehicle, and a vehicle follower capable of following behind an in-path vehicle at a predetermined interval. The system also includes an auto-resume accelerator capable of accelerating the host vehicle to the set speed, a traffic density determiner capable of determining a value for traffic density, and an auto-resume acceleration limiter capable of limiting the rate of acceleration caused by the auto-resume accelerator based on the value of traffic density generated by the traffic density determiner.
An advantage of the present invention is that the acceleration of an ACC equipped vehicle with auto-resume is adjusted to account for the density of vehicles around that vehicle. This will allow for a more acceptable driving experience for the driver of the ACC vehicle by avoiding too fast of acceleration in heavy traffic situations and too slow of acceleration in light traffic situations.
Another advantage of the present invention is that a slower acceleration rate for an auto-resume may be more appropriate in heavy traffic situations since the likelihood of unexpected maneuvers by nearby vehicles that causes them to move in-path of the ACC vehicle are increased. This, then, allows more time for the ACC system to detect a new in-path vehicle and switch to a vehicle following mode.